Estimation of DC numbers in blood and assessment of the purity of isolated pcDCs and myDCs. DCs were identified in peripheral blood mononuclear cells by their lack of labeling for a cocktail of CD3, CD14, CD16, and CD19, but positive labeling for HLA-DR (panel Ai; R2). The DCs were subsequently separated into 2 populations on the basis of labeling for CD11c (panel Aii). Following isolation with BDCA-1 and BDCA-4, the plasmacytoid (panel B) and myeloid (panel C) DCs were highly purified. Contaminating T lymphocytes are located in the upper left quadrant. For all infection studies, only DC preparations that contained fewer than 1% contaminating T lymphocytes were used. For functional studies, the majority of DC preparations had less than 1% contaminating T lymphocytes; however, 3 myDC and 3 pcDC preparations had 1% to 5% contaminating T lymphocytes. The percentage of cells within each quadrant is shown.